Field of the Invention
Embodiments of the invention relate to display devices, in particular touch sensor integrated type display devices.
Discussion of the Related Art
In recent years, various input devices, such as a keyboard, a mouse, a track ball, a joystick, and a digitizer, have been used to construct interfaces between users and home appliances or information and communication devices. However, when the user makes use of these input devices, the user's dissatisfaction increases because the user is required to learn how to use the input devices and the input devices occupy space, thereby making it difficult to achieve a high level of completeness in the products. Thus, a demand for a convenient and simple input device for the display device capable of reducing erroneous operations is increasing. In response to the increased demand, a touch sensor has been proposed to recognize information when the user inputs information by directly touching the screen or approaching the screen with his or her hand or a pen while he or she watches the display device.
The touch sensor has a simple configuration capable of reducing the erroneous operations. The user can also perform an input action without using a separate input device and can quickly and easily manipulate a display device through the contents displayed on the screen. Thus, the touch sensor has been applied to various display devices.
The touch sensor may be classified into an add-on type touch sensor, an on-cell type touch sensor, and an integrated type (or in-cell type) touch sensor, depending on its structure. The add-on type touch sensor may be configured such that the display device and a touch panel including the touch sensor are individually manufactured, and then the touch panel may be attached to an upper substrate of the display device. The on-cell type touch sensor may be configured such that the touch sensor may be directly formed on the surface of an upper glass substrate of the display device. The integrated type touch sensor may be configured such that the touch sensor may be mounted inside the display device to thereby achieve a thin profile display device and increase the durability of the display device.
The add-on type touch sensor causes the thickness of a display device to increase because the add-on type touch sensor has a structure in which the add-on type touch sensor is mounted on the display device. Further, visibility of the display device is reduced because of a reduction in a brightness of the display device resulting from the increased thickness.
The on-cell type touch sensor shares the glass substrate with the display device because the on-cell type touch sensor has the structure in which the on-cell type touch sensor is formed on the surface of the glass substrate of the display device. Therefore, a thickness of the display device using the on-cell type touch sensor is less than a thickness of the display device using the add-on type touch sensor. However, the entire thickness of the display device implementing the on-cell type touch sensor increases because of use of a touch driving electrode layer, a touch sensing electrode layer, and an insulating layer for insulating the touch driving electrode layer and the touch sensing electrode layer which constitute the on-cell type touch sensor.
Accordingly, development directions of the touch sensor are focused on the integrated type touch sensor in that it is possible to achieve a thin shape of the display device and enhance a durability of the display device, thereby resolving the problems of the add-on type and on-cell type touch sensors. The integrated type touch sensor may be classified into a light type touch sensor and a capacitive touch sensor depending on a method for sensing a touched portion. The capacitive touch sensor may be sub-classified into a self capacitive touch sensor and a mutual capacitive touch sensor.
The self capacitive touch sensor forms a plurality of independent patterns in a touch area of a touch sensing panel and measures changes in a capacitance of each independent pattern, thereby deciding whether or not a touch operation is performed. The mutual capacitive touch sensor crosses X-axis electrode lines (for example, driving electrode lines) and Y-axis electrode lines (for example, sensing electrode lines) in a touch/common electrode formation area of a touch sensing panel to form a matrix, applies a driving pulse to the X-axis electrode lines, and senses changes in voltages generated in sensing nodes defined as crossings of the X-axis electrode lines and the Y-axis electrode lines through the Y-axis electrode lines, thereby deciding whether or not a touch operation is performed.
In the mutual capacitive touch sensor, a mutual capacitance generated in touch recognition of the mutual capacitive touch sensor is very small, but parasitic capacitances between gate lines and data lines constituting the display device are very large. Therefore, it is difficult to accurately recognize touch positions because of the parasitic capacitances.
Further, because a plurality of touch driving lines for a touch driving operation and a plurality of touch sensing lines for a touch sensing operation have to be formed on the common electrode for the multi-touch recognition of the mutual capacitive touch sensor, the mutual capacitive touch sensor requires a very complex line structure.
On the other hand, because the self capacitive touch sensor has a simpler line structure than the mutual capacitive touch sensor, touch accuracy may increase. Hence, the self capacitive touch sensor has been widely used, if necessary or desired.
A related art liquid display device (hereinafter referred to as “touch sensor integrated type display device”), in which a self capacitive touch sensor is embedded, is described below with reference to FIGS. 1 to 2C. FIG. 1 is a planar view illustrating a related art touch sensor integrated type display device. FIG. 2A is a planar view schematically illustrating a relation between pixel electrodes and a touch/common electrode in an area corresponding to one touch and common electrode. FIG. 2B is a planar view illustrating a region R1 shown in FIG. 2A, and FIG. 2C is a cross sectional view illustrating a region R2 shown in FIG. 2A.
Referring to FIG. 1, the touch sensor integrated display device includes an active area AA, in which touch/common electrodes are arranged and data are displayed, and a bezel area BA positioned outside the active area AA. In the bezel area BA, various wires and a source and touch driving integrated circuit 10 are disposed.
The active area AA includes a plurality of touch/common electrodes Tx11 to Tx14, Tx21 to Tx24, . . . , and Tx51 to Tx54, and a plurality of touch routing wires TW11 to TW14, TW 21 to TW24, . . . , and TW51 to TW54 connected to the plurality of touch/common electrodes Tx11 to Tx14, Tx21 to Tx24, . . . , and Tx51 to Tx54, respectively. The plurality of touch/common electrodes Tx11 to Tx14, Tx21 to Tx24, . . . , and Tx51 to Tx54 are arranged in a first direction (e.g. x-axis direction) and a second direction (e.g. y-axis direction) which cross each other. The plurality of routing wires TW11 to TW15, TW 21 to TW25, . . . , and TW81 are arranged in parallel to each other in the second direction.
The plurality of touch/common electrodes Tx11 to Tx14, Tx21 to Tx24, . . . , and Tx51 to Tx54 are formed by dividing a common electrode of a display device. The plurality of touch/common electrodes Tx11 to Tx14, Tx21 to Tx24, . . . , and Tx51 to Tx54 are operated as common electrodes during a display mode for displaying data, and operated as touch/common electrodes during a touch mode for perceiving touch positions.
The bezel area BA is positioned outside the active area AA, and includes various wires and the source and touch driving integrated circuit 10. The source and touch driving integrated circuit 10 supplies display data to data lines in synchronization with driving of gate lines (not shown) of the display device, and supplies a common voltage to the touch/common electrodes Tx11 to Tx14, Tx21 to Tx24, . . . , and Tx51 to Tx54 during the display mode. Also, the source and touch driving integrated circuit 10 supplies a touch driving voltage to the touch/common electrodes Tx11 to Tx14, Tx21 to Tx24, . . . , and Tx51 to Tx54, and determines touch positions at which touches are performed by scanning changes of capacitance in the touch/common electrodes before and after the touch is performed during the touch mode. The various wires disposed in bezel area BA include the touch routing wires TW11 to TW14, TW21 to TW24, . . . , and TW51 to TW54, gate lines and data lines (not shown) extended from the active area AA and connected to the source and touch driving integrated circuit 10.
As described above, when conductive objects such as fingers or stylus pens are touched on the active area AA of the touch sensor integrated type display device, it is possible to determine touch positions at which touches are performed by scanning changes of capacitance in touch/common electrodes before and after the touch is performed. More specifically, a touch driving voltage is supplied to the touch/common electrodes Tx11 to Tx14, Tx21 to Tx24, . . . , and Tx51 to Tx54 in the active area AA, and then the touch/common electrodes Tx11 to Tx14, Tx21 to Tx24, . . . , and Tx51 to Tx54 are sensed via the touch routing wires TW11 to TW14, TW 21 to TW24, . . . , and TW51 to TW54. It is possible to determine touch positions at which touches are performed by using a known touch algorithm based on changes of capacitance in the touch/common electrodes before and after the touch is performed.
However there are some problems such as a mura defect in the touch sensor integrated type display device. This is due to the fact that an electric field difference is generated in pixels according to positions of routing wires TW11 to TW14, TW21 to TW24, . . . , and TW51 to TW54 connected the touch/common electrodes Tx11 to Tx14, Tx21 to Tx24, . . . , and Tx51 to Tx54. That is, because the positions of the routing wires TW11 to TW14, TW21 to TW24, . . . , and TW51 connected to the touch/common electrodes Tx11 to Tx14, Tx21 to Tx24, . . . , and Tx51 to Tx54 are different from each other, electric fields at particular positions are different. Hereinafter, the reason of the mura defect generation is more detailed described with reference to FIGS. 2A to 2C.
In the FIGS. 2A to 2C, it is omitted to describe constructional elements disposed under the data lines to obviate complication of description. In example of FIG. 2A, one touch/common electrode Tx11 has a size corresponding to three pixels in a horizontal direction and the three pixels in a vertical direction, that total 9 pixels P11 to P13, P21 to P23 and P31 to P33.
Referring to FIGS. 2A to 2C, data lines DL1 to DL3 disposed on a gate insulation layer GI covering the gate lines GL1 to GL3. The Pixel electrodes P11 to P13, P21 to P23 and P31 to P33 are disposed on an insulation layer covering the data lines DL1 to DL6. The routing wire TW11 is disposed on a first passivation layer PAS1 covering the pixel electrodes P11 to P13, P21 to P23 and P31 to P33. The other routing wires TW12 to TW14, TW21 to TW24, . . . and TW51 to TW54 shown in FIG. 1 are also disposed on the first passivation layer PAS1. The touch/common electrode Tx11 is disposed on a second passivation layer PAS2 covering the routing wire TW11. The other touch and common electrodes Tx12 to Tx14, Tx21 to Tx24, . . . and Tx51 to Tx54 shown in FIG. 1 are also disposed on the second passivation layer PAS2. The touch and common electrode Tx11 is connected to the routing wire TW11 exposed through a contact hole CH1 of the second passivation layer PAS2.
In the touch sensor integrated type display device, there are two regions R1 and R2 in one touch and common electrode (for example, Tx11). The first region R1 is a region where the routing wire TW11 is disposed to overlap the data line DL1. The second region R2 is a region where no routing wire is disposed to overlap the data line DL1.
For example, in the touch/common electrode Tx11, the routing wire TW11 overlaps the first data line DL1 passing though the touch and common electrode Tx11. However there are no routing wire to be overlapped with the second to third data lines DL2 to DL3 passing though the touch/common electrode Tx11. Accordingly, the first data line DL1 overlaps the first routing wire TW11 and is disposed to be neighbored to the pixel electrodes P11, P21 and P31. Electric field between the first data line DL1 and the pixel electrodes P11, P21 and P31 is blocked by the routing wire TW11 as shown in FIGS. 2A and 2B. Accordingly, the pixel electrodes P11, P21 and P31 are not affected by a data voltage supplied to the second to third data lines. However, the pixel electrodes P12, P22, P32; P13, P23, and P33 are affected by data voltages supplied to the second to third data lines DL2 to DL3 because the second to third data lines DL2 to DL3 are not overlapped with the routing wire as shown in FIGS. 2A and 2C. Accordingly, a mura defect is generated in the touch and common electrode Tx11 of the sensor integrated type display device.
Also, there is no parasitic capacitance in the region R1 because the electric field between the first data line DL1 and the pixel electrode P11, P21 and P31 is blocked by the routing wire TW11. However, there are parasitic capacitances in the region R2 because the electric field between the second to third data lines DL2 to DL3 and the pixel electrode P12, P22, P32; P13, P23, and P33 affect a liquid crystal layer as shown in FIGS. 2A and 2C.
The parasitic capacitance obstructs normal driving of liquid crystal molecules during a display operation, thereby causing display defects due to a light leakage